Help with an excercise.

[Dstrayex]

I'm learning C++ from a book and one of the excercises is this-



The framing program writes the mostly blank lines that separate the borders from the greeting one character at a time. Change the program so that it writes all the spaces needed in a single output expression.

*****Code******

#include <iostream>
#include <string>

// say what standard-library names we use
using std::cin;         using std::endl;
using std::cout;        using std::string;

int main()
{
    // ask for the person's name
    cout << "Please enter your first name: ";

    // read the name
    string name;
    cin >> name;

    // build the message that we intend to write
    const string greeting = "Hello, " + name + "!";

    // the number of blanks surrounding the greeting
    const int pad = 1;

    // the number of rows and columns to write
    const int rows = pad * 2 + 3;
    const string::size_type cols = greeting.size() + pad * 2 + 2;

    // write a blank line to separate the output from the input
    cout << endl;

    // write rows rows of output
    // invariant: we have written r rows so far
    for (int r = 0; r != rows; ++r) {

        string::size_type c = 0;

        // invariant: we have written c characters so far in the current row
        while (c != cols) {

            // is it time to write the greeting?
            if (r == pad + 1 && c == pad + 1) {
                cout << greeting;
                c += greeting.size();
            } else {

                // are we on the border?
                if (r == 0 || r == rows - 1 ||
                    c == 0 || c == cols - 1)
                    cout << "*";
                else
                    cout << " ";
                ++c;
            }
        }

        cout << endl;
    }

    return 0;
}

Sorry it might be hard to understand since you haven't been following what's happening in the book. But if you know how to do it it would be cool if you can explain it.